1. Related Technical Fields
Related technical fields include traffic situation determination systems, methods, and programs that determine a traffic situation on a road.
2. Related Art
On-vehicle navigation devices, personal digital assistants (PDAs), mobile information devices such as a mobile phone, personal computers, and the like, are capable of displaying a map of a desired area to a user. The maps are displayed by storing information on roads such as a general road and an expressway, facility names, and the like as map information in various storage devices, downloading the map information from a server, and/or the like.
Traffic information such as traffic jam information of a displayed road may also be provided in order to improve the user's convenience. As a new system of acquiring the traffic information, a probe car system, in which a running vehicle acts as a sensor (probe) to gather probe information in a probe center and thereby produce the traffic information, is currently under research. The probe information may include a current position, travel path, speed, and the like, measured by the probe vehicle. For example, Japanese Patent Application Publication No. JP-A-2004-234649 (e.g., page 5 and FIG. 2) discloses a system that accumulates probe information gathered from a probe car, generates traffic information by performing a statistical process on the accumulated information, and provides the traffic information to a terminal such as a navigation device or a PC.
Also, in the related art, a vehicle position can be specified using a mobile phone installed in a vehicle. Specifically, the current position of the mobile phone in a mobile phone communication network can be identified by a known enhanced observed time difference (E-OTD) method, a time difference of arrival (TDOA) method, a cell-ID method, and/or the like. The information center acquires the information via the mobile phone communication network, whereby the position of the phone (an thus the vehicle) can be specified on the information center side without performing communication with the vehicle.